Compression test on msx150

Hello, in the msx150 manual it says that the compression should be 140psi plus or minus 14psi at sea level.....can anyone tell me or tell me how to figure out what it should be at 1080m above sea level?

On the left is the number of feet you are above sea level. On the right is the factor to use when calculating. So lets say your at 3543 (1080 meters) feet above sea level and normally your cylinder would read 140psi at sea level. Take 140 (normal expected compression)x0.907. This would give you an expected reading of about 126 psi on your gauge at altitude.